1. Field
The present invention relates to photography, and more specifically systems and methods of taking pictures with digital cameras.
2. Background
Digital cameras have helped to simplify many of the complexities of picture taking for novices, while at the same time offering a wide variety of controls for sophisticated users. Novice users can set their digital cameras to an automatic mode, allowing them to simply point and shoot while taking pictures. More advanced users can control and adjust a wide variety of camera parameters to optimize the camera settings for the given conditions or achieve various special effects in their photographs.
One advantage of digital cameras is that a user can instantaneously review a photograph which has just been taken. Since the images are stored digitally, it is simply a matter of retrieving the picture from the camera's memory to be displayed on the digital display or viewfinder. However, even though a photograph can be easily and conveniently reviewed, minor imperfections in the image may not be apparent due to the small size of the view finder. It is oftentimes difficult to tell whether the camera had appropriate lighting or exposure settings when viewing a digital photograph on a tiny electronic display or viewfinder. The photographer may not be aware of minor imperfections due to the parameter settings of the camera until the photograph is printed out, thus resulting in a lost photo opportunity.
There are precautions that can be taken to avoid ending up with a flawed photo taken with improper settings or parameters. To avoid photos which are under exposed or over exposed, photographers can take a series of pictures which are exposure bracketed, sometimes called auto exposure bracketing (AEB). Typically three to five pictures are taken, each picture being taken at a different exposure setting. In this way, the photographer can review each of the pictures taken, and select the photo with the best exposure setting. Digital cameras may also include other bracketing options such as white balance bracketing which ensures that the photo has the proper blue/amber bias and magenta/green bias.
Another problem which can occur in photography is a picture taken slightly out of focus. To avoid photographs which are out of focus, some sophisticated cameras have been equipped to use a focus bracketing procedure in which the camera takes three exposures with varying focus points. A drawback of focus bracketing is that while it may save a picture that would have otherwise had the primary subject out of focus, it does not help to avoid depth of field problems. Photographers using manually adjustable analog or digital cameras can use manual depth of field (DOF) bracketing to increase the likelihood of ending up with a photograph which has the amount of depth of field that the photographer desires. Depth of field bracketing involves taking several pictures with different DOFs by manually varying both the aperture and the shutter speed to have multiple exposures taken at the same illumination level, but with different DOFs. Although DOF bracketing may be done manually by photographers, no camera today incorporates the ability to have the camera automatically take a series of exposures where the illumination level remains constant, but the DOF varies.
One major drawback in attempts to use DOF bracketing is that the camera must be manually adjusted for each photograph, a process which takes considerable time sometimes resulting in changes in the lighting level of the subject, considerable movement of the subject or other condition changes in the scene. When the light level in the scene to be photographed changes, it is either very difficult or impossible to take the additional photos needed for DOF bracketing. Moreover, quite often the photographer wants some portions of the photo to be in focus, while other portions of the photo are purposefully out of focus, in order to achieve a desired effect. There is no method or system for DOF bracketing which is automatic and which allows a portion of the picture to be purposefully left out of focus.
What is needed is a method and system of DOF bracketing which adjusts the camera rapidly enough to avoid changes in the lighting or position of the subject, and is suitable for leaving portions of the photo purposefully out of focus.